The present disclosure relates generally to gas turbine engine load bearing cases. More particularly, the present disclosure relates to systems for mounting heat shields between a structural frame and a flow path fairing in a turbine exhaust case.
Turbine Exhaust Cases (TEC) typically comprise structural frames that support the very aft end of a gas turbine engine. In aircraft applications, the TEC can be utilized to mount the engine to the aircraft airframe. In industrial gas turbine applications, the TEC can be utilized to couple the gas turbine engine to an electrical generator. A typical TEC comprises an outer ring that couples to the outer diameter case of the low pressure turbine, an in inner ring that surrounds the engine centerline so as to support shafting in the engine, and a plurality of struts connecting the inner and outer rings. As such, the TEC is typically subject to various types of loading, thereby requiring the TEC to be structurally strong and rigid. Due to the placement of the TEC within the hot gas stream exhausted from a combustor of the gas turbine engine, it is typically desirable to shield the TEC structural frame with a fairing that is able to withstand direct impingement of the hot gases. The fairing additionally takes on a ring-strut-ring configuration wherein the vanes are hollow to surround the frame struts. The structural frame and the fairing can each be made of materials optimized for their respective functions.
In order to further protect the TEC structural frame, heat shields are disposed between the frame and the fairing. The heat shields provide thermal protection to the structural frame by inhibiting conductive heat transfer from the fairing to the structural frame. The heat shields thereby assist in limiting thermal expansion and distortion of the TEC structural frame, which may adversely affect alignment of components interacting with the TEC, such as the low pressure turbine case and shaft. It is desirable to attach the heat shield within the TEC to prevent vibration of the heat shield and the resulting wear vibration produces. Conventionally, heat shields have been welded to the TEC structural frame. Welded joints are, however, undesirable due to the resulting inability to easily remove the heat shields. Heat shields have also been “spring-loaded” or biased against the frame or fairing to prevent vibration. However, such designs are not robust enough for industrial gas turbine engine applications. There is, therefore, a need for improved coupling arrangements for heat shields in gas turbine engine structural components.